Agency staff at the huge factory in Cowley, near Oxford, vented their anger on union leaders, pelting them with fruit before storming out of the plant saying they felt “betrayed”.

Unions attacked BMW, the German owners of the Mini, accusing them of using workers as “cannon fodder”, and called on the Government to intervene to give immediate rights to agency workers.

Derek Simpson, joint general secretary of Unite telephoned Business Secretary Lord Mandelson pressing him to introduce a European directive on agency workers so those affected by the Cowley cuts would receive redundancy pay, while joint leader Tony Woodley fumed that the treatment of the workers had been “disgraceful”.

He said: “We have demanded an urgent meeting with the chairman of BMW in light of today’s dismissal of 850 workers at the end of a shift. This is no way to treat workers, and I personally shall be pushing BMW to revoke this decision and give people their jobs back.”

BMW said: “While Mini has been weathering the economic downturn, it is not immune from the challenges of the current situation.”